Blood Type and Sex Linked Inheritance

[Pages:20]Blood Type and Sex Linked Inheritance

The Classic Example of Codominance in Humans is BLOOD TYPE

Gene that controls ABO blood type codes for an enzyme that makes a glycolipid on blood cells Two alleles (IA and IB) (call them "A" and "B") are codominant Third allele (IO) (call it "O") is recessive to A and B

Possible Genotypes for Blood Types

If the Phenotype: A

Genotype(s): AA, AO

If the Phenotype: B

Genotype(s): BB,BO

If the Phenotype: AB

Genotype(s): AB

If the Phenotype: O

Genotype(s): OO

Your blood type is determined by A and/or B proteins on red blood cell surfaces

Blood Tests are done by adding antibodies to the sample

Which blood type clots with both anti-A

and anti-B? _A__B__

Which blood type doesn't clot with anti-

A or anti-B? __O___

? Do you know what YOUR blood type is?

The Rhesus Factor You are either R(+) or R(-) for the

Rhesus Protein

A problem for Rh (-) moms ...

?What if baby is Rh (+)?

? Doctor can give Mom a shot (Rhogam, at about 28 weeks) that removes or hides R(+) cells from Mom's bloodstream

A Real Problem: Mom is Type B, Dad is Type O ... Baby is Type AB. Is

this possible?

?Cross: _B_O__ X _O_O__

MOM

B

Remember, when in doubt, heterozygous is

O more likely

O BO OO

O BO OO

Sex Chromosomes: the 23rd pair in humans

All others (122) are called

autosomes

Boy Girl

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